NASA Scientists Discover Unexpected Mineral on Mars

Scientists have discovered an unexpected
mineral in a rock sample at Gale Crater on Mars,
a finding that may alter our understanding of
how the planet evolved.
NASA's Mars Science Laboratory rover, Curiosity,
has been exploring sedimentary rocks within Gale
Crater since landing in August 2012. In July
2015, on Sol 1060 (the number of Martian days
since landing), the rover collected powder drilled
from rock at a location named "Buckskin."
Analyzing data from an X-ray diffraction
instrument on the rover that identifies minerals,
scientists detected significant amounts of a
silica mineral called tridymite.
This detection was a surprise to the scientists,
because tridymite is generally associated with
silicic volcanism, which is known on Earth but
was not thought to be important or even present
on Mars.
The discovery of tridymite might induce
scientists to rethink the volcanic history of Mars,
suggesting that the planet once had explosive
volcanoes that led to the presence of the
mineral.
Scientists in the Astromaterials Research and
Exploration Science (ARES) Division at NASA's
Johnson Space Center in Houston led the study.
A paper on the team's findings has been
published in the Proceedings of the National
Academy of Sciences.
"On Earth, tridymite is formed at high
temperatures in an explosive process called
silicic volcanism. Mount St. Helens, the active
volcano in Washington State, and the Satsuma-
Iwojima volcano in Japan are examples of such
volcanoes. The combination of high silica
content and extremely high temperatures in the
volcanoes creates tridymite," said Richard Morris,
NASA planetary scientist at Johnson and lead
author of the paper. "The tridymite was
incorporated into 'Lake Gale' mudstone at
Buckskin as sediment from erosion of silicic
volcanic rocks."
The paper also will stimulate scientists to re-
examine the way tridymite forms. The authors
examined terrestrial evidence that tridymite could
form at low temperatures from geologically
reasonable processes and not imply silicic
volcanism. They found none. Researchers will
need to look for ways that it could form at lower
temperatures.
"I always tell fellow planetary scientists to
expect the unexpected on Mars," said Doug
Ming, ARES chief scientist at Johnson and co-
author of the paper. "The discovery of tridymite
was completely unexpected. This discovery now
begs the question of whether Mars experienced
a much more violent and explosive volcanic
history during the early evolution of the planet
than previously thought."